JP2018135487A - Polymer, electrolyte membrane, and solid polymer fuel cell - Google Patents

Abstract

（Ｒ１〜Ｒ１０は各々独立にＨ、Ｃ１〜４のアルキル基又はフェニル基；Ａｒはイオン官能基を有する２価の芳香族基；前記イオン官能基は鎖状もしくは環状の４級アンモニウムカチオン又はスルホ基、燐酸基或いはカルボキシ基）
【選択図】なし[Problem] To provide a polymer having excellent chemical durability and excellent solubility in a solvent.
A polymer having a repeating unit represented by formula (1) and an electrolyte membrane thereof.

(R1 to R10 are each independently H, C1-4 alkyl group or phenyl group; Ar is a divalent aromatic group having an ionic functional group; the ionic functional group is a linear or cyclic quaternary ammonium cation or sulfo group. Group, phosphoric acid group or carboxy group)
[Selection figure] None

Description

  The present invention relates to a polymer, a precursor, a catalyst layer, and a polymer electrolyte fuel cell.

  Polymer polymer fuel cells (PEFCs), which have attracted attention in recent years, are expected to be used as next-generation power generation systems with high efficiency and low environmental load.

  The present inventors have conducted various studies on the polymer for the electrolyte membrane for PEFCs. For example, Patent Document 1 has a specific hydrophilic portion and a specific hydrophobic portion as a proton conductive material having high swelling resistance and high proton conductivity in which ion exchange groups are densely integrated. A proton conductive material having a repeating unit containing a specific cyclic compound in at least one of the hydrophobic parts is disclosed.

JP2016-44242A

  As a polymer for an electrolyte membrane used in a polymer electrolyte fuel cell, a polymer excellent in chemical durability against radicals and alkalis is required for long-term operation of the fuel cell. On the other hand, from the viewpoint of chemical durability, when the main chain of the polymer is fully aromatic, the solubility in a solvent is lowered, and the handling property during film formation may be deteriorated.

  The present invention has been made in view of the above circumstances, and includes a polymer excellent in chemical durability and solubility in a solvent, an electrolyte membrane containing the polymer, and the electrolyte membrane. An object of the present invention is to provide a polymer electrolyte fuel cell.

  The polymer according to the present invention has a repeating unit represented by the following general formula (1).

（一般式（１）中、Ｒ^１〜Ｒ^１０は、各々独立に、水素原子、炭素原子数が１以上４以下のアルキル基、又は、フェニル基であり、Ａｒはイオン官能基を有する２価の芳香族基である。複数あるＲ^１〜Ｒ^１０及びＡｒは互いに同一であっても異なっていてもよい。）

(In General Formula (1), R ^{1 to} R ¹⁰ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a phenyl group, and Ar is a divalent group having an ionic functional group. A plurality of R ^{1 to} R ¹⁰ and Ar may be the same or different from each other.)

  In one embodiment of the polymer of the present invention, the Ar is one or more selected from the following general formula (2) to the following general formula (9).

（一般式（２）〜一般式（９）中のＲ^ｂは、各々独立にイオン官能基であり、ｎはアルキル鎖の炭素原子数を表し、各々独立に、１以上１２以下の整数である。）

( ^Rb in the general formula (2) to the general formula (9) each independently represents an ionic functional group, n represents the number of carbon atoms in the alkyl chain, and each independently represents an integer of 1 or more and 12 or less. .)

  In one embodiment of the polymer of the present invention, the ionic functional group is one or more selected from the following general formula (10) to the following general formula (13).

（一般式（１０）〜一般式（１３）中、Ｒ^１１〜Ｒ^１３は、各々独立に、炭素原子数が１以上６以下の、直鎖、分岐、又は環状のアルキル基であり、Ｒ^１４〜Ｒ^１７は、各々独立に、炭素原子数１以上４以下のアルキル基、フェニル基、又は、置換基としてメチル基を有してもよいフェニル基であり、Ａ−は、１価、又は２価以上のアニオンである。）

(In General Formula (10) to General Formula (13), R ^{11 to} R ¹³ are each independently a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, and R ¹⁴ To R ¹⁷ are each independently an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a phenyl group which may have a methyl group as a substituent, and A- is monovalent or 2 An anion having a valence higher than that.)

（一般式（１４）〜一般式（１９）中のＲ^ａは、各々独立にスルホ基、リン酸基、又はカルボキシ基である。） In one embodiment of the polymer of the present invention, the Ar is at least one selected from the following general formula (14) to the following general formula (19).

(R ^a in the general formula (14) to the general formula (19) is each independently a sulfo group, a phosphate group, or a carboxy group.)

The present invention provides an electrolyte membrane comprising the polymer according to the present invention.
The present invention also provides a polymer electrolyte fuel cell comprising the electrolyte membrane according to the present invention.

  According to the present invention, there are provided a polymer excellent in chemical durability and solubility in a solvent, an electrolyte membrane containing the polymer, and a polymer electrolyte fuel cell including the electrolyte membrane. can do.

1 shows ¹ H-NMR before and after the alkali resistance evaluation results of the polymer of Example 1. FIG. 2 shows ¹ H-NMR before and after the results of evaluation of radical resistance of the polymer of Example 1. FIG. FIG. 3 shows the results of a power generation test of the membrane electrode assembly produced using Example 1. FIG. 4 shows the durability test results of the membrane electrode assembly produced using Example 1. FIG. 5 is ¹ H-NMR of compound 6 obtained in step (vii) in Example 1. FIG. 6 is ¹ H-NMR of compound 7 obtained in step (viii) in Example 1. FIG. 7 is ¹ H-NMR of polymer 1 obtained in step (ix) in Example 1. FIG. 8 is ¹ H-NMR of polymer 3 (invention) obtained in step (x) in Example 1.

Hereinafter, the polymer, the electrolyte membrane, and the polymer electrolyte fuel cell according to the present invention will be described in detail in order.
In the present specification, R ^{1 to} R ⁿ represent each of R ¹ , R ² ..., And R ⁿ unless otherwise specified.

1. Polymer The polymer according to the present invention has a repeating unit represented by the following general formula (1).

（一般式（１）中、Ｒ^１〜Ｒ^１０は、各々独立に、水素原子、炭素原子数が１以上４以下のアルキル基、又は、フェニル基であり、Ａｒはイオン官能基を有する２価の芳香族基である。複数あるＲ^１〜Ｒ^１０及びＡｒは互いに同一であっても異なっていてもよい。）

(In General Formula (1), R ^{1 to} R ¹⁰ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a phenyl group, and Ar is a divalent group having an ionic functional group. A plurality of R ^{1 to} R ¹⁰ and Ar may be the same or different from each other.)

The polymer of the present invention is excellent in chemical durability and solubility in a solvent.
The action of the polymer of the present invention having these effects is unclear, but is estimated as follows.
A polymer widely used as a polymer for an electrolyte membrane has an ether bond or other hetero atom in the main chain (for example, Patent Document 1). In addition, many polymers have aliphatic hydrocarbons in the main chain. As a result of intensive studies, the present inventors have found that a polymer having an ether bond in the main chain may be decomposed in the presence of an alkali or a radical, and a polymer having an aliphatic hydrocarbon in the main chain is It was found that it may be decomposed in the presence of radicals.
From such a point of view, the present inventors examined a polymer in which the main chain is wholly aromatic, that is, each of the elements constituting the main chain is contained in the aromatic ring. However, such polymers have excellent resistance to alkalis and radicals, but are easy to π-π stacking and have low solubility in solvents. For example, an electrolyte membrane is formed. There was a problem.
As shown in the general formula (1), the polymer of the present invention has a structure in which a divalent aromatic group having an ionic functional group and a spirobifluorene skeleton are alternately repeated. In the polymer, each element constituting the main chain skeleton belongs to an aromatic ring or is a spiro atom having no hydrogen atom, and the main chain skeleton does not have an ether bond. It is estimated that decomposition is suppressed and chemical durability is excellent. In addition, the spirobifluorene skeleton has a structure in which two fluorenes are twisted at almost right angles through a spiro atom, and the fluorene skeleton constitutes a main chain, so that the entire main chain has a large number of bends. It is in a state. Therefore, since the planarity of the main chain is lowered, it is presumed that π-π stacking is inhibited and the solubility in a solvent is excellent.

R ^{1 to} R ¹⁰ in the general formula (1) are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a phenyl group. Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, a propyl group, and a tert-butyl group. In the polymers of the present invention, from the viewpoint of enhancing solubility, at least one of R ¹ and R ¹⁰ is preferably an alkyl group, more preferably R ¹ and R ¹⁰ is an alkyl group, In addition, R More preferably, ¹ and R ¹⁰ are tert-butyl groups. By having a bulky substituent in at least one of R ¹ and R ¹⁰ , polymer aggregation due to π-π stacking or the like is suppressed and solubility in a solvent is improved. On the other hand, R ^{1 to} R ⁸ are each independently preferably a hydrogen atom or a methyl group, and more preferably a hydrogen atom.

  Ar in the general formula (1) is a divalent aromatic group having an ionic functional group. The aromatic ring constituting the aromatic group constitutes the main chain of the polymer. Therefore, the polymer of the present invention is excellent in resistance to alkalis and radicals. The aromatic ring constituting the aromatic group may be a heterocyclic ring containing O (oxygen atom), N (nitrogen atom), and S (sulfur atom) in addition to an aromatic hydrocarbon ring composed of a carbocyclic ring. . As the aromatic hydrocarbon ring, in addition to a benzene ring, condensed polycyclic aromatic hydrocarbon groups such as naphthalene ring, tetralin ring, indene ring, fluorene ring, anthracene ring, phenanthrene ring; A cyclic hydrocarbon group is mentioned. The heterocyclic ring includes 5-membered heterocycles such as furan, thiophene, pyrrole, oxazole, thiazole, imidazole, and pyrazole; 6-membered heterocycles such as pyran, pyrone, pyridine, pyrone, pyridazine, pyrimidine, and pyrazine; And condensed polycyclic heterocycles such as indole, carbazole, quinoline, isoquinoline, acridine, phthalazine, quinazoline, quinoxaline, and benzodithiophene.

  Ar has an ionic functional group as a substituent of the aromatic ring. The ionic functional group may be directly bonded to the aromatic ring, or may be bonded via an alkyl group having 1 to 12 carbon atoms. In the case where the ionic functional group is an acidic group described later, it is preferably directly bonded to the aromatic ring. On the other hand, when the ionic functional group is a quaternary ammonium group or imidazolium group described later, it is preferably bonded to the aromatic ring via an alkyl group.

  In the polymer of the present invention, Ar is selected from the following general formula (2) to the following general formula (9) from the viewpoint of excellent chemical durability and solubility in a solvent. It is preferable that it is 1 or more types.

（一般式（２）〜一般式（９）中のＲ^ｂは、各々独立にイオン官能基であり、ｎはアルキル鎖の炭素原子数を表し、各々独立に、１以上１２以下の整数である。）

( ^Rb in the general formula (2) to the general formula (9) each independently represents an ionic functional group, n represents the number of carbon atoms in the alkyl chain, and each independently represents an integer of 1 or more and 12 or less. .)

  When the polymer of the present invention is a porous polymer, n in the general formula (8) is preferably 1 or 2.

The ionic functional group in Ar is not particularly limited, and may be appropriately selected from known ionic groups according to the application. When proton conductivity is imparted to the polymer of the present invention, the ionic functional group is acidic such as a sulfo group (—SO ₃ H group), a phosphoric acid group (—HPO ₃ group), a carboxy group (—COOH group), etc. It is preferably a group, and among them, a sulfo group is preferable. In addition, when anion conductivity is imparted to the polymer of the present invention, the ionic functional group is preferably a quaternary ammonium group or an imidazolium group. The quaternary ammonium group is preferably a quaternary alkyl ammonium group. The quaternary alkylammonium group includes those in which alkyl groups bonded to a nitrogen atom are bonded to form a ring structure. Specific examples include an azaadamantyl group and a quinuclidinium group.

  Since the polymer of the present invention has excellent durability against hydroxide ions, it can be suitably used as an anion exchange membrane. From such a viewpoint, the polymer of the present invention can be suitably used as an anion conductive polymer. In this case, the ionic functional group is preferably a quaternary ammonium group or an imidazolium group.

  From such a viewpoint, the polymer of the present invention preferably has one or more ionic functional groups selected from the following general formula (10) to the following general formula (13).

（一般式（１０）〜一般式（１３）中、Ｒ^１１〜Ｒ^１３は、各々独立に、炭素原子数が１以上６以下の、直鎖、分岐、又は環状のアルキル基であり、Ｒ^１４〜Ｒ^１７は、各々独立に、炭素原子数１以上４以下のアルキル基、フェニル基、又は、置換基としてメチル基を有してもよいフェニル基であり、Ａ⁻は、１価、又は２価以上のアニオンである。）

(In General Formula (10) to General Formula (13), R ^{11 to} R ¹³ are each independently a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, and R ¹⁴ To R ¹⁷ are each independently an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a phenyl group which may have a methyl group as a substituent, and A ⁻ is monovalent or 2 An anion having a valence higher than that.)

Preferred examples of the linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms in R ^{11 to} R ¹³ include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, A hexyl group, a cyclohexyl group, etc. are mentioned. Examples of the alkyl group having 1 to 4 carbon atoms in R ^{14 to} R ¹⁷ include a methyl group, an ethyl group, a propyl group, and a butyl group. Examples of the phenyl group that may have a methyl group as a substituent include 3,5-dimethylphenyl group.
Moreover, A < ^- > in General formula (10)-General formula (13) is a counter anion, and is not restricted to a monovalent thing, The thing more than bivalence may be sufficient. The A ⁻ is preferably an inorganic anion, specifically, chloride ion (Cl ⁻ ), bromide ion (Br ⁻ ), iodide ion (I ⁻ ), bicarbonate ion (HCO ₃ ⁻ ). , Carbonate ion (CO ₃ ²⁻ ), hydroxide ion (OH ⁻ ) and the like.

  Moreover, when an ionic functional group is an acidic group, it is preferable that said Ar is 1 or more types selected from following General formula (14)-following General formula (19).

（一般式（１４）〜一般式（１９）中のＲ^ａは、各々独立にスルホ基、リン酸基、又はカルボキシ基である。）

(R ^a in the general formula (14) to the general formula (19) is each independently a sulfo group, a phosphate group, or a carboxy group.)

  The polymer of this invention may have a site | part different from the structural unit represented by the said General formula (1) in the range which does not impair the effect of this invention. Examples of such a site include a site where an ionic functional group is not introduced into Ar of the structural unit represented by the general formula (1).

In the polymer of the present invention, the number of repeating units represented by the general formula (1) is not particularly limited, but is usually 2 or more and 1,000 or less, and preferably 10 or more and 1,000 or less. .
The mass average molecular weight (Mw) of the polymer of the present invention is not particularly limited, but is usually 1,000 or more and 300,000 or less.
The number average molecular weight (Mn) of the polymer of the present invention is not particularly limited, but is usually 1,000 or more and 300,000 or less.

  Moreover, when applying the polymer of this invention as an electrolyte membrane for fuel cells, it is preferable that the ionic functional group density in the said polymer is 0.5 mmol / g or more and 4 mmol / g or less.

  Since the polymer of the present invention is excellent in solubility in a solvent, particularly in tetrahydrofuran, chloroform and the like, it is excellent in handling properties such as film formation. Moreover, since it is excellent also in chemical durability, it can be suitably used for an electrolyte membrane for a polymer electrolyte fuel cell.

  The method for synthesizing the polymer of the present invention is not particularly limited, but a preferred example is the method of Scheme 1 below.

（スキーム１中、Ｒ^ａは、一般式（２）〜下記一般式（９）におけるＲ^ａと同様であり、Ｒ^ｂは、一般式（１）中の、Ｒ^１及びＲ^１０に相当する置換基である。）

(In Scheme 1, ^{R a} is the same as ^{R a} in formula (2) to the following general formula (9), ^{R b} has the general formula (1) in, corresponding to ^{R 1} and ^{R 10} substituents Group.)

In the example of Scheme 1 above, a compound (B) having a brominated spirobifluorene skeleton is synthesized from the compound (A) having a desired substituent R ^b (step (i) to step (vii)). Separately from this, a compound (Ar) in general formula (1) is reacted with bromide (C) having a desired aromatic ring (benzene ring in the example of Scheme 1) by reacting with bis (pinacolato) diborane ( D) is synthesized (step (viii)). After polymerizing the compound (B) and the compound (D), a polymer represented by the general formula (1) is obtained by introducing a desired ionic functional group (step (ix) to step (ix)). xi)).
In addition, since the detail of each said reaction condition is as the below-mentioned Example, description here is abbreviate | omitted.

2. Electrolyte Membrane The electrolyte membrane according to the present invention is suitably used as an electrolyte membrane of a polymer electrolyte fuel cell, and includes the polymer according to the present invention. By including the polymer of the present invention, an electrolyte membrane excellent in durability can be obtained. The method for producing the electrolyte membrane is not particularly limited, but since the polymer according to the present invention is excellent in solubility in a solvent, a solution of the polymer is prepared, and a coating film is formed using a conventionally known coating means, and dried. By doing so, an electrolyte membrane containing the polymer according to the present invention can be obtained.

3. Polymer electrolyte fuel cell The polymer electrolyte fuel cell according to the present invention includes the electrolyte membrane of the present invention. Since the polymer electrolyte fuel cell of the present invention includes the electrolyte membrane containing the polymer according to the present invention, the polymer electrolyte fuel cell has durability capable of withstanding long-term operation.
The polymer electrolyte fuel cell usually has at least an anode, a cathode, and an electrolyte membrane, and may have other components such as a catalyst as necessary. In the present invention, other configurations such as an anode, a cathode, and a catalyst are not particularly limited, and generally known configurations as solid polymer fuel cells can be appropriately selected and used.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. Note that the present invention is not limited by these descriptions.

(Example 1: Synthesis of polymer)
The synthesis of the polymer will be described. For the step number, refer to Scheme 1 above.
<Step (i)>
4-tertbutylphenylboronic acid (11.6 g, 65 mmol), 2-bromobenzaldehyde (9.25 g, 50 mmol), tetrakistriphenylphosphine palladium (0) (1733 mg, 1.5 mmol), sodium carbonate (15.9 g, 150 mmol) was mixed with a mixed solvent of dimethoxyethane (65 ml) / water (30 ml). The mixed solution was bubbled with nitrogen (10 minutes) in a closed system and reacted at 80 ° C. for 12 hours under nitrogen. After evaporating the solvent in the reaction solution with an evaporator, the residue is dissolved in dichloromethane and water. The organic layer is washed several times with water using a separatory funnel, and then dichloromethane is evaporated using an evaporator. The obtained residue was purified by column chromatography (developing solvent: hexane: chloroform = 4: 1) to obtain the target Compound 1 (9.77 g) shown below in a yield of 82%.

<Step (ii)>
4-tertbutylphenylboronic acid (9.8 g, 55 mmol), 2-iodobromobenzene (14.1 g, 50 mmol), tetrakistriphenylphosphine palladium (0) (1733 mg, 1.5 mmol), sodium carbonate (15.9 g) , 150 mmol) is dissolved in a mixed solvent of dimethoxyethane (65 ml) / water (30 ml). The mixed solution was bubbled with nitrogen in a closed system (10 minutes) and reacted at 80 ° C. for 24 hours under nitrogen. After evaporating the solvent in the reaction solution with an evaporator, the residue is dissolved in dichloromethane and water. The organic layer was washed several times with water using a separatory funnel, and then dichloromethane was evaporated using an evaporator. The obtained residue was purified by column chromatography (developing solvent: hexane) to obtain the target Compound 2 (7.37 g) shown below in a yield of 51%.

<Step (iii)>
Compound 1 (7.15 g, 30 mmol) and ferrocene (186 mg. 1 mmol) were dissolved in acetonitrile (10 ml), a tertbutyl hydroperoxide (3 g, 33 mmol) decane solution was added, and the mixture was reacted at 70 ° C. for 12 hours. Thereafter, a tert-butyl hydroperoxide (3 g, 33 mmol) decane solution was again added to the reaction solution and reacted at 70 ° C. for 12 hours. After the reaction, acetonitrile was evaporated by an evaporator, and the residue was purified by column chromatography (hexane: chloroform = 3: 1). The purified compound 3 was recrystallized in hexane to obtain the following highly pure compound 3 (4.86 g) in a yield of 68%.

<Step (iv) to Step (v)>
Compound 2 (5.78 g, 20 mmol), magnesium (5.34 g, 22 mmol) and iodine (100 mg) are mixed with ultra-dehydrated THF (20 ml) and refluxed for 6 hours under nitrogen. The Grignard solution obtained by this reaction was cooled to room temperature, compound 3 (4.77 g, 20 mmol) was added, and the mixture was allowed to react at room temperature for 3 hours. Water was slightly added to the reaction solution, and after stirring for 5 minutes, the solvent was evaporated with an evaporator.
The obtained residue was purified by column chromatography (developing solvent: chloroform: hexane = 1: 1) to obtain the following compound 4 (4.77 g, 17 mmol) in a yield of 85%.

<Step (vi)>
Compound 4 (6.70 g, 15 mmol) was mixed with acetic acid and dissolved at 80 ° C. Concentrated hydrochloric acid was added to this solution and allowed to stir for 60 minutes. At this time, the target white solid precipitated. The precipitated solid was collected by filtration and washed several times with water. As a result, the following compound 5 (6.17 g) having a high purity was obtained in a yield of 96%.

<Step (vii)>
Compound 5 (6.0 g, 14 mmol) and iron (III) chloride (162 mg, 1 mmol) were dissolved in chloroform (100 ml). Bromine (6.39 g, 40 mmol) was added, and the reaction was performed at room temperature for 4 hours. Next, an aqueous sodium thiosulfate solution was added to the reaction solution until the red color of bromine faded. Thereafter, the organic layer was washed with water three times with a separatory funnel. After the chloroform in the organic layer was evaporated by an evaporator, the column chromatography was purified by column chromatography (developing solvent: developed with hexane and then developed with hexane: chloroform = 4: 1), and the target compound 6 ( 7.63 g) was obtained with a yield of 93%. A ¹ H-NMR spectrum of the compound 6 is shown in FIG.

<Step (viii)>
3,5-dibromotoluene (10.7 g, 43 mmol), bis (pinacolato) diborane (25.4 g, 100 mmol), potassium acetate (19.6 g, 200 mmol), tetrakistriphenylphosphine palladium (0) (2.30 g, 2 mmol) was mixed with ultra-dehydrated dioxane (100 ml). The mixed solution was bubbled with nitrogen for 10 minutes, and the reaction was performed under nitrogen at 80 ° C. for 18 hours. Dioxane in the reaction solution was evaporated with an evaporator, extracted with dichloromethane, and washed with brine. After evaporating dichloromethane in the organic layer with an evaporator, the residue was purified by chromatography (developing solvent: first hexane, then hexane: chloroform = 1: 1) to obtain the target compound 7 (10.5 g) shown below in a yield. Obtained at 71%. A ¹ H-NMR spectrum of the compound 7 is shown in FIG.

<Step (ix)>
Compound 6 (monomer 6) (1173 mg, 2 mmol), Compound 7 (monomer 7) (688 g, 2 mmol), tetrakistriphenylphosphine palladium (0) (231 mg, 0.2 mmol), potassium carbonate (1.38 g, 10 mmol) ) And 18-crown-6 (52.8 mg, 0.2 mmol) were dissolved in a mixed solvent of toluene (20 ml) / water (8 ml). The reaction solution was bubbled with nitrogen for 10 minutes or more in a closed system, and then reacted at 100 ° C. for 60 hours under nitrogen. The solution after the reaction was transferred to a separatory funnel to remove the aqueous layer, and then the organic layer was washed 3 times with 1M hydrochloric acid and then 3 times with water. Toluene in the organic layer was concentrated with an evaporator and reprecipitated in methanol. Thereafter, the obtained solid was dissolved in chloroform and reprecipitated in hexane and acetone in the same manner to remove monomers and oligomers. The obtained solid was vacuum dried at 100 ° C. to obtain the target polymer 1 (490 mg) shown below. The ¹ H-NMR of the polymer 1 is shown in FIG.

<Step (x)>
The polymer 1 (206 mg) is dissolved in chlorobenzene (15 ml), and N-bromosuccinimide (214 mg, 3 mmol) and azobisisobutyronitrile (2 mg) are added. The reaction solution was reacted at 110 ° C. for 4 hours under closed system nitrogen.
The solution after the reaction was concentrated with an evaporator and then reprecipitated in methanol. The obtained solid was dissolved in chloroform and reprecipitated once more. The obtained solid was vacuum dried at 40 ° C. to obtain the target polymer 2 (201 mg).

<Step (xi)>
The polymer 2 (200 mg) is dissolved in tetrahydrofuran (10 ml), and a 30 wt% trimethylamine aqueous solution (0.5 ml) is added. After the reaction solution was reacted at room temperature for 1 hour, the solvent was removed with an evaporator. The obtained solid is immersed in a 1 M sodium hydroxide solution at room temperature for 24 hours to exchange the anion in the polymer from bromide ion to hydroxide ion. Thereafter, the solid is recovered by filtration, immersed in pure water for 6 hours, and then recovered again. The obtained solid was vacuum-dried at 40 ° C. to obtain Polymer 3 (180 mg) having a structural unit represented by General Formula (1). The ¹ H-NMR of the polymer 3 is shown in FIG.

[Alkali resistance evaluation]
The polymer 3 obtained in Example 1 was immersed in a 1M NaOH solution and stirred at 80 ° C. for 1 week. ¹ H-NMR of the polymer 3 before and after immersion was measured. The results are shown in FIG. From the comparison of ¹ H-NMR before and after immersion, no major change was observed in the peak derived from the main chain (broad peak around 6.5 to 8 ppm in FIG. 1), and the ionic functional group (trimethylammonium group) Although there is a shift in the broad peak around 3 to 3.5 ppm from the origin (peak a in FIG. 1), there is no change in the relative integration ratio. On the other hand, it became clear that it had the outstanding durability.

[Radical resistance evaluation]
The polymer 3 obtained in Example 1 was immersed in a 3 wt% H ₂ O ₂ + FeSO ₄ 10 ppm solution and stirred at 60 ° C. for 8 hours. ¹ H-NMR of the polymer 3 before and after immersion was measured. The results are shown in FIG. From the comparison of ¹ H-NMR before and after immersion, although a change was observed in the broad peak around 3 to 3.5 ppm derived from the trimethylammonium group (peak a in FIG. 2), the peak derived from the main chain (FIG. 1). The broad peak in the vicinity of 6.5 to 8 ppm in the inside was not significantly changed, and it was revealed that the radical resistance was excellent.

[Solvent solubility evaluation]
When the polymer 3 obtained in Example 1 was added to various solvents and the solubility was evaluated, it was revealed that the polymer 3 had a high solubility of 50 mg / ml or more in chloroform and tetrahydrofuran (THF). . Moreover, it showed excellent solubility of 20 mg / ml or more in a mixed solvent (1: 3) of 1-propanol and tetrahydrofuran, which is widely used for dispersing catalyst particles. Since the polymer of the present invention can be dissolved in at least these solvents, it is excellent in handleability during film formation. On the other hand, the polymer 3 is insoluble in methanol used as a battery fuel, and is suitable as a material for a fuel cell.

[Fuel cell performance evaluation]
Using the polymer 3 obtained in Example 1 as an ionomer, a solid polymer fuel cell (hereinafter referred to as a liquid fuel cell) using methanol as a fuel was produced.
As the electrolyte membrane, a pore filling membrane (thickness 25 μm) in which a polyethylene porous substrate was filled with a crosslinked polyvinylbenzylammonium chloride was used. The anode electrode catalyst layer was prepared by spray-coating platinum ruthenium-supported carbon and the above polymer 3 dispersion (solvent: THF) on one side of the electrolyte membrane (metal support amount 1.9 mg / cm ² ). The cathode electrode catalyst layer was prepared by spray-coating a platinum iron carbon free capsule and a dispersion solution of the polymer 3 (solvent: THF: 1-propanol = 3: 7) on the opposite surface of the membrane (metal loading amount) 1.1 mg / cm ² ). After the membrane electrode assembly (MEA) thus produced was adhered by hot pressing at 100 ° C. and 2 kN for 1 minute, an anode diffusion layer Sigracet 29AA (manufactured by SGL Carbon; carbon paper without PTFE (polytetrafluoroethylene) treatment), The MEA was sandwiched between cathode diffusion layers Sigracet 29BC (manufactured by SGL carbon; carbon paper with MPL (microporous layer)) and set in a single cell (electrode area 5 cm ² ) manufactured by ElectroChem, Inc. A 2M methanol / 2M potassium hydroxide (KOH) mixed fuel was supplied to the anode at 10 ml / min, and humidified oxygen (100 RH) was supplied to the cathode at 500 ml / min. . The results are shown in FIG. Further, the operation for 10 hours or more per day was continued, and after 3 days and 1 week, a power generation test similar to the above was performed to evaluate the durability of the MEA. FIG. 3 shows the results of the first day, and FIG. 4 shows the result of combining the results after 3 days and 1 week.
As shown in FIG. 3, the liquid fuel cell obtained by using the polymer 3 of the present invention has the performance of an open circuit electromotive voltage of 0.8 V and an output of 70 mW / cm ² . Also, as shown in FIG. 4, the open circuit electromotive voltage and the output hardly changed even after the power generation of 10 hours or more per day was continued for one week. Therefore, the use of polymer 3 as an ionomer is highly durable. A liquid fuel cell can be produced.

Claims (6)

The polymer which has a repeating unit represented by following General formula (1).

(In General Formula (1), R ^{1 to} R ¹⁰ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a phenyl group, and Ar is a divalent group having an ionic functional group. A plurality of R ^{1 to} R ¹⁰ and Ar may be the same or different from each other.) The polymer according to claim 1, wherein the Ar is one or more selected from the following general formula (2) to the following general formula (9).

( ^Rb in the general formula (2) to the general formula (9) each independently represents an ionic functional group, n represents the number of carbon atoms in the alkyl chain, and each independently represents an integer of 1 or more and 12 or less. .) The polymer according to claim 1 or 2, wherein the ionic functional group is one or more selected from the following general formula (10) to the following general formula (13).

(In General Formula (10) to General Formula (13), R ^{11 to} R ¹³ are each independently a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms, and R ¹⁴ To R ¹⁷ are each independently an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a phenyl group which may have a methyl group as a substituent, and A ⁻ is monovalent or 2 An anion having a valence higher than that.) The polymer according to claim 1, wherein Ar is one or more selected from the following general formula (14) to general formula (19).

(In the general formula (14) to the general formula (19), each R ^a is independently a sulfo group, a phosphate group, or a carboxy group.)   An electrolyte membrane comprising the polymer according to any one of claims 1 to 4.   A polymer electrolyte fuel cell comprising the electrolyte membrane according to claim 5.

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